In the computer industry, hard disk data storage elements or memory are generally made from aluminum or an aluminum alloy. These hard disk memory components have certain properties or characteristics which make them commercially practicable products. For example, hard disk components should be flat and smooth or have an ability to be super finished to near atomic smoothness. The disk should also be free of defects such as holes, pits, digs, scratches and mounds. The disk should also be thin so that as many disks as possible can be packaged or placed in a disk drive.
Fabricating a disk which is thin and has a low mass is also easier on the drive motor. The disk should also be hard and quite stiff. High stiffness, as measured by the modulus of elasticity, allows the disk to avoid harmonic vibration. One other attribute that the disks preferably have is a lower cost. With an increasing emphasis towards higher quality and lower cost, various alternative disk substrates have been explored.
One alternative to aluminum substrates for hard disks is the use of nonmetallic materials such as glass, and glass/ceramic. Various methods have been developed for processing these materials to improve physical and mechanical properties such as tempering the substrate to increase strength. Glass tempering is usually regarded as the strengthening of glass through the variable cooling of the material, e.g. cooling the outside of the substrate more quickly than the inside.
For example, Michalik et al, U.S. Pat. No. 3,883,339 teaches the tempering glass sheets while they are clamped and vertically suspended first during heating and then cooling. Kaufman et al, U.S. Pat. No. 3,844,757 teaches a method of heating the glass sheet clamped and vertically suspended in a furnace. Ballard, U.S. Pat. No. 4,111,675 teaches the vertical suspension of glass sheets in a fluidized bed during heat exchange.
Nishitani et al, U.S. Pat. No. 5,009,694 teaches a method of heat treating glass plates to strengthen the peripheral regions of the plates. Further, Dumbaugh, Jr., U.S. Pat. Nos. 4,102,664 and 5,342,426 disclose methods of producing glass sheets for use in various applications by requiring alkali metal free glass. Finally, Hopkins et al, U.S. Pat. No. 4,566,893 provides a method for the film processing and annealing of glass CRT panels.
The trend in personal computers towards compact or notebook size computers has led to a need for greater data memory and durability. Increased memory and durability comes with the use of a hard drive having a higher structural integrity and physical quality as well as the ability to place higher densities on the drive. Additionally, economies of scale, require cost-effective higher performing hard drives.
As a result, the need for disks of higher structural integrity and physical properties as well as the need for higher data densities and cost-effective higher performance has lead to a need for hard drives having significant improvements. Glass is one exemplary substrate which provides significant advantages of durability, hardness and surface finish. But glass is hard and expensive to process, that is to edge properly and get flat. Flatness improvements are necessary for smaller head disk spacing and reduced signal to noise ratio.
Thus there is a need for improved methods of processing nonmetallic disks to increase structural integrity, physical properties, data storage capacity, and miniaturization.